Issue 61

F. Ferrian et al., Frattura ed Integrità Strutturale, 61 (2022) 496-509; DOI: 10.3221/IGF-ESIS.61.33

Figure 5: Details of the mesh, constraints and loads used in the FEM model to evaluate the accuracy by Eqn. (16).

The failure stress estimations provided by FFM and CCM for a finite width geometry through Eqns. (14)-(16) are finally plotted in Fig. 6. As clearly highlighted in this figure, CCM and FFM fit well the data, especially for  > 0.5. As  decreases the percent discrepancy increases up to 20 % for   0.1. On the contrary, the accuracy of the PM reveals questionable for this data set, especially for large scale-sizes.

Figure 6: Circular hole in a finite tensile slab: size effects by FFM (continuous line), CCM (dashed line), PM (dash-dotted line) and experiments on PUR [21]. The finite crack advancement  c / l ch , provided by Eqn. (11) multiplying  c with  , and the process zone length a pc , given similarly by Eqn. (13), are represented in Fig. 7. The absolute values of the two sizes are quite different between each other. Nevertheless, the trend with respect to the dimensionless size  is somehow similar. Considering FFM,  c decreases from the value 2 l ch /  until it reaches a minimum and then it tends to 2 l ch / [  (1.12) 2 ] as  increases. Analogously, a pc decreases until it reaches a minimum for   0.4, and then it increases monotonically. The deviation between the process zone length in CCM and the finite crack advancement in FFM may be explained considering that whereas a pc is a fictitious crack, since cohesive stresses are present,  c is a “real” crack, because the new crack lips are stress free.

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